Drivers have been paying attention to fuel efficiency of a vehicle due to the recent surge in oil prices and roughly are aware of the fuel efficiency of the vehicle as “mileage (km)/lubrication amount (L)”.
The fuel efficiency, which is separately designated in vehicle models, merely represents fuel consumption under specific driving condition and does not represent fuel consumption considering driving habits for each driver. The fuel efficiency of the vehicle has been considerably affected by usual driving habits of a driver, such as a frequency of a sudden start and a sudden acceleration, a driving speed, and the like and has a considerable difference depending on a road condition or a driving condition. In particular, the case in which the vehicle is driven while a window of the vehicle is opened has been recognized as a main factor of reducing the fuel efficiency of the vehicle.
Therefore, a need exists for a technology of sensing an opened degree of the window of the vehicle, predicting the reduction in the fuel efficiency, and warning the reduction in the fuel efficiency to the driver.